JPH11287824A - Probing system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the stimulus of low impedance and the response of high impedance, by giving stimulus signal to a device under test with a probe cable having a diode and a resistor. SOLUTION: A stimulus circuit working as a power source supplies a transistor Q1 with the signal of a reversal buffer 104 upon a control signal 101 by way of a base resistor 6. In the case of measurement which stimulus is not necessary, the transistor Q1 is switched to OFF by the control signal 101 and a diode D1 is inversely biased by the resistor R4 connected to a power source Vs and it functions as a voltage meter and/or an oscilloscope measuring a voltage VDUT. On the other hand, when the transistor Q1 functions by the control signal 101 forwarding high level, a current passes from the voltage +Vs through the transistor Q1 and a resistor 5, via a cable 107 and a wire 108 to the diode D1, and voltage stimulus is given so that the conduction state, resistor RDUT capacity, etc., of the device to be measured can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to test and measurement equipment and, more particularly, to a single cable single point stimulus response probing system and method for use in test and measurement equipment.

[0002]

2. Description of the Related Art Circuit testing is an essential element in circuit design, circuit analysis, and circuit troubleshooting. Many devices are available that perform various test functions. For example, digital multimeters, oscilloscopes, and logic analyzers provide voltmeter functions such as voltage, resistance, and continuity; component test functions such as diode operation, capacitance, and inductance; and logic circuit analysis, sine wave and Including, but not limited to, generating arbitrary waveform pulses, and counting frequencies;
It is part of the equipment used to perform various circuit test functions. Usually, in a circuit test, a response is measured by stimulating a circuit. Voltmeter functions and component testing are examples of stimulus measurements, and logic analyzer and oscilloscope measurements are examples of response measurements.

[0003] Usually, a stimulus response test and measurement device is connected to a device under test (DUT) by a coaxial cable. DU
T is any circuit, component or logic device to be analyzed or tested. Examples include discrete components such as resistors, capacitors, and diodes, and application specific ICs (ASI
There are integrated circuit components and logic circuits including C). The single cable configuration described above places a large capacitive load on the DUT (typically greater than 100 pF) and limits the measurement to a limited bandwidth. For high bandwidth measurements, typically 2
Two coaxial cables are required. One cable connects the stimulus source to the DUT, and another cable connects the DUT to the response measurement circuit. This configuration allows higher bandwidth signal measurements, but requires the user to manage multiple sets of test cables.

Typically, for high bandwidth applications, the stimulus output is low impedance (typically 50 or 75 ohms), thus requiring a low impedance connection between the stimulus source and the DUT. When measuring high bandwidth responses, the connection between the DUT and the response measurement circuit should be high impedance (typically 100k-10M ohms, <20p) to eliminate or minimize distortion of the signal being measured.
F). The way to load the DUT in this way is
Generally, it can be used to measure frequencies below about 500 MHz. In this configuration, a component for electrically isolating the capacitive load of the cable from the DUT is usually arranged at the tip of the probe cable. However,
Such components at the tip of the probe increase the impedance between the DUT and the test equipment, making it impossible to connect the stimulus circuit to the DUT using that cable. Therefore, it is desirable to provide a single test cable that enables both low impedance stimulus measurements and high impedance response measurements in high bandwidth applications.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved probing system and method for use with test and measurement equipment.

[0007]

SUMMARY OF THE INVENTION The present invention provides an improved probing system and method for use with test and measurement equipment. The single-cable, single-point, stimulus-response probing system disclosed herein can be used in portable test equipment and any test or measurement equipment that measures both high and low impedance circuits. .

The present invention is a probing system and method capable of both low impedance stimulation measurements and high impedance response measurements, the probing system providing a cable and a first stimulation signal to the cable. And a response circuit configured to receive the output of the cable. The cable is basically two signal wires and a ground shield. In a first embodiment, the cable has a first diode and a resistor at or near the tip of the probe.

[0009] A second embodiment of the probing system adds another diode and signal wire to the cable, adding many embodiments of the stimulation circuit. A first embodiment of the stimulation circuit is configured to send a first stimulation signal to both diodes in the probe. The response circuit is configured to receive the output of the cable, as in the first embodiment.

A second embodiment of the stimulus circuit adds a push-pull amplifier circuit and two additional diodes to the stimulus circuit, the additional circuit configured to send a local feedback signal to the first amplifier. Is done. A local feedback signal is obtained from the output of the stimulation circuit.

A third embodiment of the stimulus circuit includes the push-pull amplifier of the previous embodiment and adds a second amplifier located in the response circuit. The second amplifier is configured to receive a signal from the probe as an input, buffer the signal, and send the signal as loop feedback to a first amplifier located in the stimulation circuit. The loop feedback signal represents the voltage signal at the tip of the probe, but is buffered by the second amplifier before the first
To the amplifier.

A fourth embodiment of the stimulus circuit eliminates the push-pull amplifier circuit and, according to the output of the first amplifier, conducts enough current to drive a diode located in the probe.

The present invention also conceptualizes to provide a method for providing stimulation to a single cable probing system capable of both low impedance stimulus measurement and high impedance response measurement including the following steps. You can also. First, a stimulus signal is provided to a probe cable that includes a first diode and a resistor. Next, a response signal is received by a response circuit, the response signal being provided from a probe cable. In a second embodiment, a second diode is added to the probe cable.

The present invention has many advantages, only a few of which are described below by way of example only. An advantage of the single cable single point stimulus response probing system and method is that it provides the ability to perform both low impedance stimulus measurements and high impedance response measurements using a single probe cable. is there.

Another advantage of the single cable single point stimulus response probing system and method is that
The use of a single cable reduces the complexity and time required to perform test and measurement functions on various circuits and components.

Another advantage of the single cable, single point, stimulus response probing system and method is that it allows for the testing and measurement of multiple passive devices and active circuit elements.

Another advantage of the single cable, single point, stimulus response probing system and method is that it allows for testing and measurement of the circuit.

Another advantage of the single-cable, single-point, stimulus-response probing system and method is that the design is simple, reliable in operation, and the design lends itself to economical mass production.

Another advantage of the single cable single point stimulus response probing system and method is that application specific ICs (ASICs) for economical mass production.
It is useful for implementation above.

Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description.

The components in the drawings are not necessarily to scale, and are exaggerated to clearly illustrate the principles of the present invention.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The single cable, single point, stimulus response probing system and method of the present invention can be implemented using discrete components,
It can also be implemented above. Further, single cable single point stimulus response probing systems may benefit from single cable probing systems, such as, but not limited to, portable multimeters, oscilloscopes, frequency counters, circuit analyzers, etc. It can be used in connection with any test measurement application that can undergo the test.

Referring now to FIG. 1, there is shown a block diagram of a test and measurement device 11 including a single cable, single point, stimulus response probing system 100 of the present invention. The test and measurement device 11 may be, but is not limited to, for example, a digital multimeter, a volt / ohm meter, a logic probe, a frequency counter, an oscilloscope, or a device capable of performing analysis and measurement of circuits and components. . The measuring device 11 includes components well known to those skilled in the field of test and measuring devices. The measuring device 11
For example, it includes a logical interface 12, through which the processor 13, the memory 1
4 and the input / output interface 16 communicate. Also,
The logical interface 12 is in communication with the measuring device 18.

The measurement device 18 includes a single cable single point stimulus response probing system 100, hereinafter referred to as a probing system 100. Probing system 100 further includes a stimulation circuit 110, a response measurement circuit 120, and a probe 130. Probe 1
Reference numeral 30 is a probe cable including, for example, components described in detail below. Stimulation circuit 110 and response measurement circuit 120 are also in communication with logic interface 12.
The foregoing elements in probing system 100 together make up the present invention.

Referring to FIG. 2, there is shown a first embodiment of the single cable, single point, stimulus response probing system 100 of FIG. Probe 130 illustratively includes signal wires 108 and 1
09. Also, the ground shield 111
Including. At the probe end of the cable, that is, at the end connected to the device under test (DUT), there is a diode D1 on wire 108 and a resistor R1 on wire 109. Resistance R1
Connects a DUT (shown here with a resistor R _DUT and a power supply V _DUT ) to a measurement circuit 116 within the response measurement circuit 120. Measurement circuit 116 is a circuit that typically performs analog-to-digital conversion and analysis of the probe signal sent on line 114, as is well known in the art. The resistor R1 is the resistor R
3 together form a voltage divider, separating the DUT from the capacitive load on the signal wire 109. Ground shield 111 and resistor R3
Is connected to the ground 112.

The diode D1 is connected by a wire 108 to a stimulation circuit 110 on line 107. In this embodiment, the stimulation circuit 110 includes a transistor Q1 and
Serves as a current source including resistors R4, R5 and R6.
Exemplarily, the transistor Q1 is a bipolar junction transistor that operates in the PNP mode. For measurement functions that do not require stimulation, transistor Q1 is turned off by control signal 101. Control signal 101
Can be any pulse waveform input having a high and low level state and is sent to inverting buffer 104 over line 102. The inversion buffer 104 outputs the signal to the base resistor R6.
To Q1 via When the control signal 101 is in a low level state, that is, when the control signal 101 is off, the diode D1 is connected to the power supply (−).
Vs) is reverse-biased by a resistor R4 connected to Vs). With this configuration, the probing system 100
Can function as a voltmeter and / or oscilloscope to measure the voltage V _DUT of the _DUT . Since the diode D1 is reverse-biased, a large load is not applied to the DUT.

When the transistor Q1 is operated by the control signal 101 going to the high level, the current becomes the voltage (+
Vs) through Q1 and resistor R5, line 107 and wire 1
08 to the diode D1. In this state, by applying a voltage stimulus, the probing system 100 can be used to measure conduction, resistance, capacitance and diode voltage drop. The resistance of the R _DUT is determined by measuring the voltage across the DUT and dividing that voltage by the current provided by transistor Q1. The capacity of the DUT can be determined, for example, by measuring the rate of voltage rise in the DUT and calculating the capacity by the following equation. C = I · dt / dV

Referring now to FIGS. 3 and 4, an alternative embodiment of the single cable, single point, stimulus response probing system of FIG. 2 and for driving the diodes D1 and D2 of FIG. A schematic diagram of the stimulus circuit 110 used in FIG. This embodiment is
The probing system 100 serves as a stimulus output. A diode D2 on line 117 is added to the probe 130 of FIG. 2 and a voltage (−V
s) connected to the reverse bias resistor R4 and the voltage (+ Vs)
Is added to the resistor R7.

The response measuring circuit 120 includes the buffer amplifier 1
18 have been added. Buffer amplifier 118 is connected to line 114
Receives input from the probe 130 and provides a buffered signal output on line 122. The buffer signal represents a buffer voltage signal at the tip of the probe and is used as feedback by some alternative embodiments of the stimulation circuit 110 and will be described in detail below. Buffer amplifier 118 also includes line 1
At 19, local feedback for the inverting input is received. In this embodiment, measurement circuit 116 receives an input on line 121 via buffer amplifier 118. All other parts have the same function as in FIG.

Referring now to FIG. 4, there is shown a schematic diagram illustrating a second embodiment of the stimulation circuit 110 used by the single cable, single point stimulation response probing system of FIG. An operational amplifier (operational amplifier) 139 is used to drive the diodes D1 and D2 of FIG. 3 with the upper diode drive line 126 and the lower diode drive line 124, respectively. When transistors Q2, Q3 and Q4 are off, ie, when control signal 101 is low, diodes D4 and D5 are reverse biased by resistors R4 and R7.
This action also reverse biases diodes D1 and D2, causing probe 130 to function as a high impedance responder. Transistors Q2, Q3 and Q4 are illustratively transistors Q2 and Q3 operating in PNP mode similar to transistor Q1, and NPN
This is a bipolar junction transistor including the transistor Q4 operating in the mode.

The control signal 101 goes high, causing the transistors Q on lines 135, 134 and 151 to
When the base connection of 2, Q3 and Q4 is activated, diodes D4 and D5 become forward biased, thus diodes D1 and D2 become forward biased. As the diodes D4, D5, D1 and D2 become forward biased, the operational amplifier 139 drives the lines 126 and 124 with the stimulus signal 143 provided on the line 141.
This stimulus signal is applied to probe 13 at lines 108 and 117.
It can be any signal sent to zero, illustratively a sine wave or a pulse wave.

Referring now to FIG. 5, there is shown a schematic diagram illustrating a third embodiment of the stimulus circuit 110 of the single cable single point stimulus response probing system of FIG. The embodiment of the stimulation circuit 110 shown in FIG. 5 is improved over that shown in FIG. 4 by adding local feedback from the outputs of diodes D6 and D7 on line 138 to the operational amplifier 139. .
Transistors Q5, Q6, Q7, Q8, diode D6
To D9 and resistors R15 to R18 are added,
These make up the push-pull amplifier stage 150. Local feedback is obtained from the output of push-pull amplifier 150 at diodes D6 and D7 and is provided on line 138 to the inverting input of operational amplifier 139. The output of operational amplifier 139 on line 137 is
And D9 through push-pull amplifier circuit 150. The transistors Q5 to Q8 are bipolar junction transistors in which Q5 and Q8 operate in the PNP mode and Q6 and Q7 operate in the NPN mode. Transistors Q7 and Q8 are connected to ground 142. The feedback signal on line 138 is highly matched to the signal provided to probe 130 via upper diode drive line 126 and lower diode drive line 124. FIG.
The operation of the other components is similar to that described with respect to FIG.

Referring now to FIG. 6, there is shown a schematic diagram illustrating a fourth embodiment of the stimulus circuit 110 of the single cable single point stimulus response probing system of FIG. This alternative embodiment is similar to buffer amplifier 118 of FIG.
Line 1 using the buffered feedback signal
22 provides a loop feedback signal which is input to an inverting input 138 of an operational amplifier 139. This buffer loop feedback signal increases the accuracy of the measuring device,
Works to control output impedance. As can be seen from FIG. 6, diodes D6 and D7 have been eliminated because local feedback is no longer needed. The operation of the other components in FIG. 6 is similar to that described with respect to FIGS.

Referring now to FIG. 7, there is shown a schematic diagram illustrating a fifth embodiment of the stimulus circuit 110 of the single cable, single point, stimulus response probing system of FIG. This alternative embodiment includes diodes D1 and D1
This is an improvement over the one disclosed in connection with FIG. 6 in that it reduces the number of components required to drive 2. The transistors Q7 and Q8, the diodes D8 and D9, and the resistors R15 to R18 are omitted. Resistance R19-R
23 have been added. As the magnitude of the stimulus signal 143 on line 141 increases, the output of the operational amplifier 139 on line 137 increases, thereby increasing the current flowing through resistor R23 to ground 142. This increases the current flowing from + Vs through resistors R19 and R20.
This pulls down line 147 (the base input of transistor Q5), which provides more current to diode D1 via upper diode drive line 126 and wire 108, and thus probe 1
Supply more current to the DUT via 30.

It will be apparent to those skilled in the art that many modifications and variations can be made to the preferred embodiment of the present invention as set forth above without departing substantially from the principles of the present invention. For example, the circuits used to construct the stimulus and response measurement circuits are application specific ICs (AS
IC).

The embodiments of the present invention have been described above in detail. Hereinafter, examples of each embodiment of the present invention will be described.

[Embodiment 1] A probing system (100) capable of both low-impedance stimulus measurement and high-impedance response measurement, including a first diode (D1) and a resistor (R1). Cable (13
0) and the first stimulus signal (107)
30) to supply the first stimulus signal to the first diode (D1) and the resistor (R1).
30) a response circuit (120) configured to receive the output (114) of the probing system.

[Embodiment 2] A first signal wire (108) arranged in the cable (130) and a second signal wire (10) arranged in the cable (130).
9), a ground shield (111) located in the cable (130), and the first stimulus signal (107) located in the stimulus circuit (110) and the first diode (D1). And a first circuit (Q1) configured to supply the first circuit to the system.

[Embodiment 3] A second diode (D2) arranged in the cable (130) and configured to receive the first stimulus signal (107) from the first circuit (Q1). 2. The system of embodiment 1, further comprising:

[Embodiment 4] A probing system (100) capable of both low-impedance stimulus measurement and high-impedance response measurement, including a first diode (D1) and a second diode (D2). And a cable (130) having a resistance (R1) and a first stimulus signal (124, 126) coupled to the first diode (D1).
1) and the stimulus circuit (110) configured to supply the second diode (D2) and the stimulus circuit (11).
0), the first stimulus signal (124, 12)
6) to the first diode (D1) and the second diode (D2).
And a response circuit (120) configured to receive an output (114) of the cable (130).

[Embodiment 5] A first signal wire (108) arranged in the cable (130) and a second signal wire (10) arranged in the cable (130).
9), a third signal wire (117) disposed in the cable (130), and a ground shield (111) disposed in the cable (130). The described system.

[Embodiment 6] A push-pull amplifier (150), a third diode (D6), and a fourth diode (D7) are further provided in the stimulus circuit (110). , The third diode (D6) and the fourth diode (D7) are configured to provide a local feedback signal (318) to the first amplifier (139). The system according to aspect 4.

[Embodiment 7] A push-pull amplifier (150) arranged in the stimulus circuit (110) and a loop feedback signal (122) arranged in the response circuit (120) are connected to the stimulus circuit (120). 5. The system of embodiment 4, further comprising a second amplifier (118) configured to supply the first amplifier (139) located within the first amplifier (110).

Embodiment 8 The implementation wherein the loop feedback signal (122) represents a voltage signal on the second signal wire (109) located in the cable (130). The system according to aspect 7.

[Embodiment 9] A loop feedback signal (122) arranged in the response circuit (120) is supplied to the first amplifier (139) arranged in the stimulus circuit (110). Embodiment 5. The system of embodiment 4, further comprising a configured second amplifier (118).

Embodiment 10 A method for providing stimulus to a single cable probing system capable of both low impedance stimulus measurement and high impedance response measurement, the method comprising providing a first diode (D1) and a resistor (R1)
Providing a first stimulus signal (107) to a probe cable (130) having a response circuit (12).
0) receiving a response signal (114) from said probe cable (130) according to 0).

[0047]

As described above, by using the present invention, it is possible to provide a probing system capable of performing both low-impedance stimulus measurement and high-impedance response measurement.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a test and measurement device that includes a single cable, single point, stimulus response probing system as described herein.

FIG. 2 is a schematic diagram of a first embodiment of the single cable single point stimulus response probing system of FIG. 1;

FIG. 3 is a schematic diagram of an alternative embodiment of the single cable single point stimulus response probing system of FIG.

FIG. 4 is a schematic diagram illustrating a second embodiment of a stimulation circuit used by the single cable, single point, stimulation response probing system of FIG. 3;

FIG. 5 is a schematic diagram illustrating a third embodiment of the stimulation circuit of the single cable single point stimulation response probing system of FIG. 3;

FIG. 6 is a schematic diagram illustrating a fourth embodiment of a stimulation circuit of the single cable single point stimulation response probing system of FIG. 3;

FIG. 7 is a schematic diagram illustrating a fifth embodiment of a stimulation circuit of a third single cable single point stimulation response probing system.

[Explanation of symbols]

 110: Stimulation circuit 116: Measurement circuit 120: Response measurement circuit 130: Probe

Claims (1)

[Claims] A probing system capable of both low impedance stimulus measurement and high impedance response measurement, comprising: a cable including a first diode and a resistor; and a first stimulus signal to the cable. A stimulus circuit configured to supply and provide the first stimulus signal to the first diode and the resistor; and a response circuit configured to receive an output of the cable. A probing system.